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# blog/models.py — custom manager + ORM query examples
from django.db import models
from django.utils import timezone

class PublishedManager(models.Manager):
    """Return only published posts."""
    def get_queryset(self):
        return super().get_queryset().filter(status=Post.STATUS_PUBLISHED)

def recent(self, count=10):
        return self.get_queryset().order_by('-published_at')[:count]

class Post(models.Model):
    STATUS_DRAFT     = 'draft'
    STATUS_PUBLISHED = 'published'
    STATUS_CHOICES   = [(STATUS_DRAFT, 'Draft'), (STATUS_PUBLISHED, 'Published')]

title        = models.CharField(max_length=200)
    body         = models.TextField()
    status       = models.CharField(max_length=10, choices=STATUS_CHOICES, default=STATUS_DRAFT)
    published_at = models.DateTimeField(null=True, blank=True)

objects   = models.Manager()   # default manager
    published = PublishedManager() # custom manager

class Meta:
        ordering = ['-published_at']

# --- ORM usage examples (e.g. in a view or shell) ---

# All published posts
posts = Post.published.all()

# Filter + chain
recent = Post.published.filter(published_at__year=2024).order_by('-published_at')

# Avoid N+1: fetch author in same query
from .models import Post
posts = Post.published.select_related('author', 'category').recent(5)

# Aggregate
from django.db.models import Count
stats = Post.objects.values('status').annotate(total=Count('id'))